Initializing the "ja" culture takes 200ms when using ICU

[adamsitnik]

DateTime.Parse for "ja" culture (ONLY) is 10x times slower on Linux compared to Windows

Slower	diff/base	Windows Median (ns)	Linux Median (ns)
System.Globalization.Tests.Perf_DateTimeCultureInfo.Parse(culturestring: ja)	8.87	454.24	4029.00
System.Globalization.Tests.Perf_DateTimeCultureInfo.ToString(culturestring: da)	1.08	236.39	254.59
System.Globalization.Tests.Perf_DateTimeCultureInfo.ToString(culturestring: )	1.05	245.69	258.02
System.Globalization.Tests.Perf_DateTimeCultureInfo.ToString(culturestring: ja)	1.05	245.61	257.00
System.Globalization.Tests.Perf_DateTimeCultureInfo.ToString(culturestring: fr)	1.05	245.56	256.82

Faster	Win/Lin	Windows Median (ns)	Linux Median (ns)
System.Globalization.Tests.Perf_DateTimeCultureInfo.Parse(culturestring: da)	1.24	531.21	428.73
System.Globalization.Tests.Perf_DateTimeCultureInfo.Parse(culturestring: fr)	1.05	450.44	428.87
System.Globalization.Tests.Perf_DateTimeCultureInfo.ToStringHebrewIsrael	1.04	509.37	488.81

The contributor who wants to work on this issue should:

1. Run this simple benchmark from dotnet/performance repository and confirm the problem

git clone https://github.com/dotnet/performance.git
python3 ./performance/scripts/benchmarks_ci.py -f netcoreapp5.0 --filter System.Globalization.Tests.Perf_DateTimeCultureInfo.Parse

2. Build CoreCLR locally: https://github.com/dotnet/performance/blob/master/docs/profiling-workflow-corefx.md#Build
3. Create a small repro app: https://github.com/dotnet/performance/blob/master/docs/profiling-workflow-corefx.md#repro
4. Use PerfCollect to identify issue https://github.com/dotnet/performance/blob/master/docs/profiling-workflow-corefx.md#PerfCollect
5. Solve the issue

[tarekgh]

@adamsitnik does the results change if we change the initialization

yield return new CultureInfo("ja");

to

yield return CultureInfo.GetCultureInfo("ja");

Sorry I didn't try it myself yet. I am asking because the parsing code should be exact the same between Windows and Linux, the only difference is the calendar data we pick from the OS which should be cached if you are not recreating the culture.

[adamsitnik]

does the results change if we change the initialization

I've just tried and it does not change. I've also tested ja-JP and it does not help as well

[tarekgh]

@adamsitnik thanks for your quick try.

[tarekgh]

I looked at that and I am seeing the problem is the parse initialization time is counted as part of the measurements. The initialization should occur once for the culture. The test should really measure the parsing perf excluding the one time parse initialization. when I change the test code to:

        private static CultureInfo s_jaCulture = CultureInfo.GetCultureInfo("ja");
        private static CultureInfo s_jaJPCulture = CultureInfo.GetCultureInfo("ja-JP");

        private CultureInfo JA { get { DateTime.Parse("10/10/2010 12:00:00 AM", s_jaCulture); return s_jaCulture; }} // call parsing one time to force initialization 
        private CultureInfo JAJP { get { DateTime.Parse("10/10/2010 12:00:00 AM", s_jaJPCulture); return s_jaJPCulture; }} // call parsing one time to force initialization 

        public IEnumerable<object> Cultures()
        {
            // yield return new CultureInfo("ja");
            yield return JA;
            yield return JAJP;
            yield return new CultureInfo("fr");
            yield return new CultureInfo("da");
            yield return new CultureInfo("");
        }

I am getting the results:

Method	culturestring	Mean	Error	StdDev	Median	Min	Max	Gen 0	Gen 1	Gen 2	Allocated
Parse		637.8 ns	38.69 ns	43.00 ns	644.6 ns	570.8 ns	717.3 ns	-	-	-	-
Parse	da	654.0 ns	33.33 ns	38.38 ns	652.4 ns	578.8 ns	720.9 ns	-	-	-	-
Parse	fr	640.6 ns	30.69 ns	35.34 ns	646.5 ns	562.4 ns	685.8 ns	-	-	-	-
Parse	ja	639.9 ns	34.20 ns	39.38 ns	640.7 ns	570.5 ns	727.8 ns	-	-	-	-
Parse	ja-JP	631.3 ns	46.60 ns	51.80 ns	623.0 ns	546.3 ns	742.7 ns	-	-	-	-

It is expected the Japanese culture parsing initialization be slower than other cultures because Japanese cultures have multiple eras which required to initialize more stuff.

@adamsitnik let me know if you want me to update the test as I did here.

[adamsitnik]

I've investigated this issue and it turned out to be more complex ;)

BenchmarkDotNet JITs the code by just running the benchmark once. When it takes a lot of time, it skips further warmups and just runs the benchmark once per iteration. It does so to avoid situations where we have a benchmark that takes a lot of time to run and we run it many times just for a warmup (for example for 30s per run and six warmups = 3 minutes spend for a warmup).

The problem are benchmarks where the initialization time is high, but every next run is short. dotnet/BenchmarkDotNet#837

In this case, the first call to following code:

var culture = new CultureInfo("ja");
var result = DateTime.Parse("10/10/2010 12:00:00 AM", culture);

takes 200 ms to execute and this is not the cost of JITting the code (I've run it with CoreRT for comparison). With the performance repo settings (IterationTime = 250ms) it's considered to be long. That's why BDN runs the benchmark once per iteration. 4 us is reported due to Stopwatch resolution (this operation is to short to be just executed once before we stop the stopwatch).

The initialization time can be easily measured using the time command on Linux:

using System;
using System.Globalization;

namespace culture
{
    class Program
    {
        static void Main(string[] args)
        {
            var culture = new CultureInfo("ja");
            var result = DateTime.Parse("10/10/2010 12:00:00 AM", culture);
        }
    }
}

time dotnet run -c Release --no-build --no-restore

real	0m0,612s
user	0m0,953s
sys	0m0,097s

While for a Hello World it's just:

real	0m0,382s
user	0m0,642s
sys	0m0,070s

I am going to rename this issue and investigate the initialization time. 200ms is way too long.

[adamsitnik]

ucol_openRules takes 150ms... I <3 ICU

[adamsitnik]

FWIW I was wondering why we create a new collator based on custom text comparison rules while parsing the DateTime and debugged it to the following code:

[adamsitnik]

I've studied the ICU UCollator APIs and I cant' see any alternatives to ucol_openRules for creating an UCollator based on a list of custom rules.

Currently the only idea I have is to try to call this method with normalization disabled (UCOL_OFF instead of UCOL_DEFAULT)

[sharwell]

@adamsitnik would it help to have the ability to specify the number of warmup iterations as a manual override?

[tarekgh]

@adamsitnik I am not sure it is worth it to try optimizing the initialization time of the parsing. The reason is the main scenarios always using a single culture (e.g. CurrentCulture or InvariantCulture) which have the initialization done once and we never got any complaint about that. Also, any code using CultureInfo.GetCultureInfo will always use cached culture with the cached parsing data. I suggest closing this one until we get a real complaint.